Looking for Macro photography capabilities without spending a large sum of money? There are several ways to accomplish this, but Extensions tubes are one of the least expensive methods. The Canon 500D Close-up Lens is another.
The 500D is a small double-element lens that threads onto the filter threads on a standard (non-macro) lens. It allows that lens to be focused at a much closer distance- resulting in a higher magnification of the subject. The 500D is intended to be used on lenses with a focal length of 70mm-300mm.
Close-up lenses such as the 500D result in higher magnification when used with longer telephoto lens but shorter focal length lenses result in higher magnification when used with Extension Tubes.
I gave the 500D a try first. The quality of the 500D is very good. I found the 500D to be reasonably sharp in the center - but less sharp toward the edges.
However, I personally found the narrow focus distance range to be limiting. In addition, the quality of the pictures taken with the Canon 100mm Macro Lens were better. And I could take a wider variety of pictures with the 100mm than with the Canon 500D Close-up Lens attached to another lens.
So why would you buy the 500D?
If you are carrying a non-macro lens regardless and you want macro capabilities without the added weight and size of a macro lens, the 500D is perfect for you.
If you have a lens in the 70-300mm range and do not have the budget for a prime (fixed focal length) macro lens, the 500D is a prospect for you.
If you only want to shoot at macro distances infrequently, the Canon 500D Close-up Lens might be what you want.